<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0,user-scalable=no">
<title>mall</title>
<style>
*{
  margin:0px;
  padding:0px;
}
</style>
</head>

<body>
    <div id="app"></div>
</body>

<script>
let htmlWidth = document.documentElement.clientWidth || document.body.clientWidth
let htmlDom = document.getElementsByTagName('html')[0]
if(htmlWidth>=750){
  htmlWidth = 750
}
htmlDom.style.fontSize = htmlWidth / 20 + "px"
</script>
</html>
